Changed the rendering monad transformer from a mere type synonym to a rigid newtype, which is necessary for free-variable-intros to work as intended (always actually stack onto the preexisting variables). Made 'mathFuncDefinition' ImpredicativeType-polymorphic, so it can be used inside of more specific free-variable scopes; however at the moment this circumvents type inference rather too strongly to be acceptable.
Quite elegant way of declaring the type of free variables, using a sophisticated parametric type synonym. Something similar should be useful definitions, as well.